Effects of Sitting Position on Ventilation Distribution Determined by Electrical Impedance Tomography in Ventilated ARDS Patients

Objective: The study aimed to evaluate the improvements in pulmonary ventilation following a sitting position in ventilated ARDS patients using electrical impedance tomography. Methodology: A total of 17 patients with ARDS under mechanical ventilation participated in this study, including 8 with moderate ARDS and 9 with severe ARDS. Each patient was initially placed in the supine position (S1), transitioned to sitting position (SP) for 30 min, and then returned to the supine position (S2). Patients were monitored for each period, with parameters recorded. Main Outcome measures: The primary outcome included the spatial distribution parameters of EIT, regional of interest (ROI), end-expiratory lung impedance (Delta EELI), and parameters of respiratory mechanics. Results: Compared to S1, the SP significantly altered the distribution in ROI1 (11.29 f 4.70 vs 14.88 f 5.00%, p = 0.003) and ROI2 (35.59 f 8.99 vs 44.65 f 6.97 %, p < 0.001), showing reductions, while ROI3 (39.71 f 11.49 vs 33.06 f 6.34 %, p = 0.009), ROI4 (13.35 f 8.76 vs 7.24 f 5.23 %, p < 0.001), along with peak inspiratory pressure (29.24 f 3.96 vs 27.71 f 4.00 cmH2O, p = 0.036), showed increases. Delta EELI decreased significantly ventrally (168.3 (40.33 - 189.5), p < 0.0001) and increased significantly dorsally (461.7 (297.5 - 683.7), p < 0.0001). The PaO2/FiO(2) ratio saw significant improvement in S2 compared to S1 after 30 min in the seated position (108 (73 - 130) vs 96 (57 - 129) mmHg, p = 0.03). Conclusions: The sitting position is associated with enhanced compliance, improved oxygenation, and more homogenous ventilation in patients with ventilated ARDS compared to the supine position.